ฝัง
- เผยแพร่เมื่อ 26 ธ.ค. 2016
- Let's take a look at polymer slides to replace the linear ball bearings, steel bushings and brass nut.
Polymer bushings are quieter, self lubricating and won't damage your rail.
IGUS JSM-1012-10 Plain bushing from RS Components:
au.rs-online.com/web/p/bearin...
Anti-Backlash Nut Block from Maker Store:
www.makerstore.com.au/product/...
Download the HyperCube 3D Printer from Thingiverse:
www.thingiverse.com/thing:1752766
Buy cheap 3D Printer kits and parts from Banggood here:
goo.gl/bFyz5H
Music:
/ joakimkarud - Almost Original - วิทยาศาสตร์และเทคโนโลยี
I don't have any personal experience with the IGUS polymer bushings/bearings but i believe part of the biting issue may be because they're meant to have a uniform radial compression applied to them, whereas you applying pressure in mainly one axis of the bearing. There are IGUS bushings sold that have a metal compression sleeve already applied to it to provide this uniform compression, so maybe that could solve your problem.
Much thanks for doing the research on bearings. This is a useful resource!
- Eddy
The LM8UU bearing have groves cut into them to help grab onto whatever there housed in. I would suggest adding lips/groves on the XY joiner to hold onto the poly LM8UU's groves. Awesome video!
This video is four years old now and you've probably already worked out your bearing solution for your X-Y joiners, but just in case I thought I might share this info. IGUS makes an aluminum-cased version of their drylin bearings. With the aluminum cased version, you would be able to clamp them down tightly into your X-Y joiners without any issue. I bought four of the RJUM-01-10 bearings to replace the LM10UU bearings that I was using. They are really excellent bearings and I feel really confident recommending them. I can't take any credit for discovering them though. I became aware of these aluminum cased drylin bearings from one of Thomas Sanladerer's videos.
According to Thomas Sanladerer's video on bearings, the metal sleeve version of the IGUS bearing gives proper tolerance so there is no slop. Even with that I am not sure that it would work on the steel rod on the Y axis. Is the steel rod exactly 8mm, I can't remember if you measured them in a previous video. I haven't been able to find anyone using the IGUS bearings with the metal sleeve on a 3d printer build. It's a shame you couldn't get them to work, as I was really looking forward to seeing how they fare against the LM8UU bearings on the hypercube. I do love the new setup for the x axis and z axis.
Thanks for sharing your 3d printing adventures Tech2C!
Nice update! I've found that using short linear bushings offset (like what you did for the X axis) is in general the best solution for getting smooth movements, but with a small sacrifice of lifespan. Perhaps implementing something like this on the y axis will work out for you if you want to replace those ball bearings still. And nice change on the z axis, that new nut block looks much more rigid!
It'll be interesting to see how long these igus sleeve bushings last on the X axis. They seem nicer to use than the steel bushings but if they don't last that'll suck. Yeah the nut block is a nice option.
Well they still should last decently long, and since the whole bushing is the lubrication instead of just a coating on the metal like the old ones, they should last longer in theory. but they will lose a lot of their tolerances well before they simply quit working.
YAS, NEW BUILD LOG!
Just in time before I order bearings!
For the Y axis, (these are some more hacky methods), you could try printing bushings out of PLA or nylon(self lubricating). I use PLA carriages that run on aluminum extrusion, and those work pretty well, but they gain play over time.
The RJ4JP needs a press fit. Try the RJUM-Series. They are already in a metall casing.
You could print ridges into the holder that align with the ridges in the polymer bearing to keep it in place.
great vids, can you make a summary video of this build as you are making minor changes through the series . keep up the good work
Look up sustaglide, which is a self lubricating nylon. It's very slippery feeling and has is super low friction.
Another is Polystone M Natural, it also has a low coefficient of friction and is very abrasion resistant. Worth looking into.
Wonderful job designing and documenting your printer. Thanks so much for sharing. I'm planning to build one myself and I'm cannibalising parts off my Kossel Mini but I can't find any suppliers for the anodised aluminium tubes in Sydney. Did you order yours online? Thanks!
Have you ever planed to use Linear Rail like HIWIN? I've found some implementation to your design.
Also there is a designs with ballscrews
this is on a "or so i have heard" basis: if i am not mistaken, the drylin bearings are supposed to be a pretty snug fit in to theyr seatings, and would have a little play on the rods, if not compressed form the outside. (a precisely sized hole, not clamps ment to hold steel brearings) and need some breaking in to work as smoothly as they can.
Always enjoy watching your videos.
Cheers!
Hi, great set of videos, I have one question do u run your electronics via a PC or an attached LCD screen to the board, many thanks
At build log #5 I was wondering if you could move z-motor with cantilever to the opposite side, so all obstructions (motors) would be in the same side, that would also solve the need for long wires in build log #6. Belt "crossing" might be a bit ugly on the new front side but does not look like it would block too much. Or maybe move x-y motors, they might even be a bit more centered along a long belt and make slack/delay/etc a bit more symmetric. Anyway, your printer seems to beat most commercial offerings, cool!
i love this printer design and i am really thinking about making it soon! how up to date is the thingiverse page?
When is going to be available the complete guide and the final result?
great videos , congrats
IGUS bearings ARE NOT Concentric. That's why they appear to bind.
If you rotate one bearing in relation to the other( in the same bearing block) you will find you can make them bind or loosen up, just buy rotating only one. This is great, as it allows you to eliminate all slop, just by rotating one.
This is the secret to using more than 1 IGUS bearing in the same bearing block.
the material of the anti backlash nut looks like acetal which is commonly used for these applications
already ordered some of those Igus hope they are ok at least for x or y ...
Hello, I Love the work you do on the channel and also very excited about building the current design , but i have few queries
1) Cantilever style preferred or Dual Z- axis , planning to use 12mm Aluminium Rods (Similar Build Volume Slightly Bigger ) Desperately don't want any z-artifacts if possible
2) Planning to convert everything to 12mm rods has i have many lying around , for which what are the changes? how can i edit these Files?
3) I Dont have linear bushings , instead planning to use regular 12mm bearings , how do i modify the x-axis carriage ? For this , Prefer no Zip Ties
@Tech2C ; Why are you not using the steel sleeve type bushings on the Y axis, but LM8UU or the Igus bushings?
I'm planning to build a coreXY printer with steel sleeve bushings on both X and Y axis
The black material is called Delrin, very durable and perfect for making parts that require a thread to be included. Since the print bed always provides a load due to it's weight the brass screw will be sufficient and is very cheap to replace if ever needed, however because it is always loaded by the weight of the bed you will never notice any issues in print quality as the usable life of the brass nut will easily outlast the life of the printer. I like how you have experimented with lots of different possiblities with the build. That delrin block z axis setup would definitely be benificial on a i3 type design because there is no bed to preload the z axis.
I thought it was Delrin but the MakerStore site didn't mention the material. Cheers for watching and comments.
I used chemical metal for mine, wich i now have switched for pla printed. I use aluminium tunes with athreaded rod insert. The chemical metal ones, i made by taking a regular linear ballbearing, placed it in alginate, removed it and filled with chemical metal. Then drilled them out. They work flawlessly and are almost self greased as the material is somewhat soft and yet durable. Why i went over to printed pla is mainly due to upgrading my hand made printer with printed parts and they didnt have industrial finish, but from a movement perspective they were better than the pla, however the pla is easier to maintain.
Heya,
Have you looked at Phophor Bronze bushes ? not sure if they work with anodized Al, but the internet says its good. Plus I don't know jack mechanically...
Tech2C why you didn't use circlips to lock the igus bushings in place? It has more advantages when compared to the clamping method.
nice work
Im watching your videos because of the soundtrack.
...And also some great R&D stuff.
Haha
Yes, you can print a cylindrical adapter (to use on the Y axis) the length of two lm8uu. then use two sf1 or use Igus J bushings and ream the adapter to achieve the pre-load that you want. It will be quieter. I just ordered titanium X axis rods to play with.
Titanium for X rods? Wow impressive!
Tech2C I don't know if they will work but I want to try them. EBay item # 181478814866
What is the surface of the titanium tube? Is it anodised, or just titanium oxide? If just a naturally occurring oxide then no good as the bushing will scrape it off constantly resulting in it sticking/binding - just like aluminium.
Tech2C Titanium is crazy easy to anodise.
For the plastic bearing, you will need a stop rim in the holder. Then it will work perfectly, with them sliding around and with less pressure when clamping down. Your clamping printout is the problem, not the plastic bushings, I assume.
The anti backlash material most probably is Acetol. Great video .
I allready use the igus bushing and i have the same problem with the y-Axis als you have. For the x-Axis you can use the Igus A181SM-10-12-20, they have the same size than the Bearing Bushing you use normal. instead of using a normal aluminum shaft you can use the Igus AWMP-10 which have a hard anodized surface.
if you try to print your own bushing igus have there own filament.
Thanks for your help you do a great job
Cheers!
I am hoping to take some of this info when I modify my Wilson TS.
Anyone know of a good set of metric screws with different lengths?
The dry lubricant is a MoS2 molybdenum disulphite, the anodized aluminium is too rough for them, they should be perfect with some grease or a smooth rod .
I do want to scrap at least most of the LMUU bearings in my Prusa. The Y axis should be easy enough, I'm a little curious about the X axis since I'll have to redo the carriage.
Did you try adjusting the clamping circumference to say 45 degrees where there is the most clamping force and 0.5mm less than the bearing diameter to see how that might work? The rest of the clamping circle if you will would have a larger diameter than the rest of the clamp.
When joining the corners of the aluminum..did you consider large plates covering the corner or are the brackets you chose making it solid enough?...my end stops came in today woohoo!!!
Would a dry Teflon lube have a negative effect?
I believe the black residue you're getting on the aluminum rods may actually be very fine aluminum particles which are wearing off the rods. If you take a piece of aluminum and rub it against another hard surface repeatedly, you will begin to see a "dirty" looking build-up of these fine aluminum particles.
The coating inside the steel bearings may also be wearing off. But aluminum is a very soft material that will wear away faster than most people realize. Anodizing helps harden it a little but I think it will still wear. It would be interesting to try those same bearings on a steel rod and see if you still get the residue.
Anyway, great videos! I hope to build a printer like this someday. :)
No no, these aluminium rods are anodised. I covered this in an earlier build video, number 4 I think.
Polymer nuts and bushings works nice and quiet but you must be aware they don't glide as well and they wear much faster. I had to replace my Igus RJMP bushings (higher quality than RJ4JP) within 6 months. So I gone back to bronze bushings that can last a couple of years.
Interesting. I'll keep an eye on the sleeve bushings on the X axis.
Why did you opt to put larger stepper motors for the X and Y axis and what is the advantage over the smaller ones linked in your thingiverse page?
I've been trying to figure out the size envelope needed surrounding the gear, so the padding dimensions around the build area to upscale the build size. HELP :D
I'm working on hypercube with carbon fiber x axis. Trying to decide between igus and original steel bearings. The igus are $17 for 4 in US. Is it worth it? Did you try the steel bearings on carbon fiber?
The igus bearings are meant to be pre loaded. There is a version that is press fit into a metal tube that is a drop in replacement for the LM8UU.
That makes sense considering we only need the shaft contact area to be the Drylin material. It seems a waste to use the same material for the entire bearing.
Actually it's the same plastic bearing in a thin metal tube. Same amount of plastic.
Great vid. My only suggestion is to get lithium grease in a tube. The spray cans make such a mess.
silicon grease or Teflon grease is much better tbh
There are two versions of the IGUS bearings: canned and naked, the canned ones are much harder to crush
And bloody expensive. They are however very cool. Bronze bushings in a holder for me , they are quiet and just as good if not a bit better than a lm8uu.
I've had bad luck with that WD40 brand white lithium grease spray. It was drying out too much. I would recommend some molybdenum disulfide spray, it is black however, almost like graphite. For metal-plastic friction contact, a teflon based "dry" lubricant may work, if you find lubrication is needed.
Great info, thanks.
hey Tech2C. Thanks for the videos i been enjoying them. i'm thinking of building a 30x30x30 (build volume). I want to ask a question. Have you tried printing flexible filament with the hyper cube? That's one of the things i'm really interested at doing with this printer.
I have a video on flexible filament with my Bowden extruder. Take a look at that...
2 lead screw with a spring in the middle. tension by reducing the space containing the spring ;)
i love your build and am starting to pick up parts to make my own. I am looking to have a printable area of 360x360x400. i plan to use a dual leadscrew system for the z axis. I am worried there may be sagging in the y rods though at that length. Do you think upgrading to 10mm steel rods on the y axis would eliminate this issue?
Question: Where are you going to get a hot bed that size? Or do you just use two smaller to make the size you need?
Try it first. The X gantry is light in my configuration and might not load the 8mm Y rods enough for it to be a problem.
I really appreciate the scientific approach you have taken in this project. You mentioned in a previous video that some viewers have asked if a kit of the printed parts is available. I have no local access to quality 3D printed parts. Is there such a kit available? Thank you.
Bbox
Send me a private message.
You need a clamp for igus bushings that equally reduces the diameter as it gets clamped down. The 4 screw type shown cant achieve that.
these polymer bearings need a pressfit. sadly pressing then between two parts doesn not work :/ i have used the igus bearings with the steel sleaving on my printer with great succes
Ok great. I bought these polymer bearings as they're standard and cheap, but I like your idea to use steel sleeved versions!
the downside is that they are a tad more expensive. and i think the minimum bore is 10mm unlike the regular LM8UU which have a minimun of 6mm if i remember correctly. oh and buy the yellow tint ones, i think those are newer, better versions of the grey ones
corect. I for a while could not find out why they have alot of slop. however after some time I found that they are over sized. then when pressed in to the presion housing then they are the corect fit with no slop. go figure. :) however they should really work well. ~Russ
Could you use a regular steel bushing, cut down the middle, to assist the plastic in press fitting?
Why not print a very very slight slope on the carriage to offset the bushings?
i am planning on building a printer that is 500mmx500mmx zaxis 600mm is having a z asix on both sides going to be fine or do i need one on back also ? like videos.
Try spray silicone instead of the 3-n-1. While 3-n-1 is great stuff, I would think it is a bit "heavy" for this application. And it does cause dust to stick to the surfaces. I've found that silicone lasts just as long or longer, doesn't accumulate dust. The only problem with the spray silicone is that it is very easy to get it on everything but what you wanted lubed.
When I use the Lithium spray it gets on everything too. Very messy.
Maybe a way to use the Igus bearings on the xy joiner is to use some epoxy instead of clamping. Many Igus bearings are meant to be pressed into a precision bore that reduces the size of the Igus bearing to it's intended size. Clamping an Igus bearing into a non-precision 3D printed assembly will definitely deform it. I think it might be better to use an on-size or slightly oversize bore and use a little glue of some sort, maybe Loctite or CA or epoxy.
how many hammerhead nut do you use? in your thingiverse page, its just said 2x100pcs nut, but i think you dont need all of them right?
Have you thought of using teflon rods? instead of aluminum rods?
I would either use all aluminium and switch the parts from time to time or go for steel rods for less maintenance, basically because the nozzle movement is half of the performed movement work and need to be at least as sturdy as the rest, plus the fact that aluminium oxidises eventually in strange ways wich steel if lubricated does not and thus probably is a better choice but a tad bit more expensive
You know that you've chosen a bearing version from igus that is made to be fitted into a tube or, more exact, into a fitting hole (around IT7)? So basically you are using the bearing wrong and, as expected, it doesn't perform in the wrong use case.
Hello, my 8mm Steel rods just arrived 5 mins ago. They are 700mm long and not perfectly Straight (1mm dent)
Is this bad?
You can print out a casing for those bearings so you can clamp them normally
Karin Branham Go watch the other 14 videos in this series as an answer to why what you just said was dumb.
Getting ready to build this set up. Any issues with the amount of belts your using now that you have some run time on it?...seems like thats the only thing im worried about at this point. Thank you for a great video series by the way. i have 2 davinci's for my business and need bigger volume so here we go!!!
No problems with belts so far. After 100+ hours of use all good.
Are there any downsides to printing and tapping the block yourself instead of buying?
For the IGUS bushings, they are designed to be pressed (I.E., with an arbor press, with somewhere around 100+ pounds of force) into a bore of a very closely tolerated bore (specifically, an H7 bore, which for a 19mm hole is +0.021mm -0.000mm). This is effectively impossible to achieve with a 3D printer, but can be done with other tools. I've made a bearing block for these type of bearings, but used a Bridgeport mill and a 19mm reamer to create the hole.
The difference between this and the clamping method used in this design is that the press-fit circularly deforms the bushing, creating not only a tight fit for motion but a proper clearance for motion operation. The clamping creates an oval shaped hole, which will quickly cause binding before it is securely held, as the plastic is so flexible.
Using a high-quality linear shaft (such as the one you have in this video), there is an extremely small amount of clearance, somewhere around .012 to .03 millimeters. Over the scale of the printer, this is a negligible amount (especially for this kind of printing). I want to say that this clearance is advantageous in this application, as it will allow for less frictional forces and take up for inaccuracies in the printer construction and allow for a potentially higher printing speed. But I am not sure, I've yet to build my printer and see if that's the case.
Of course, this sort of thing isn't available to everyone, and the steel housed drop-in replacements IGUS makes are a great substitute here.
Regardless, this is a great thing you've got going, and your videos are very informative. Subscribed!
I have one clarifying question, though. You said you're using anodized rails, what kind are you using? I know IGUS makes some, and I am assuming you have theirs or an equivalent (hence me saying that they are high quality), but I'm curious to know.
Mine aren't IGUS. I bought a 3 metre length and cut it down, from a local aluminium distributor which happened to have this size anodised (most aren't). I wouldn't say high quality as there's no data sheet accompanying them.
You can buy the IGUS branded rail online from RS Components (a little expensive though)
Interesting. I would be love to see how straight they are, and how the diameter varies over their length.
Something else I am curious about--how rigid and square is the 2020 frame you built? Also in that vein, how straight is the 2020 in it? I imagine it is pretty good (maybe difficult to tell by eye), but the perfectionist in me wants to know.
Thanks for the responses, it is genuinely fascinating to hear about how other people think about and then custom build their own machines.
This build was done on-the-cheap. The 2020 extrusions I'd cut using a hand saw and mitre box. The 10mm anodised tubes appear to be straight, at least when I run them on a table they don't wobble with every rotation.
I guess there is some forgiveness with making a 3D printer, but it must be rigid/stiff. Using the aluminium corner brackets is a must in my opinion.
Hope this helps :)
Do you know why the makerstore website is not currently working?
What material are these polymer slides made from? Is it polyoxymethylene (delrin)?
Check the link in the description, it's made from their iglidur material.
do you live in Australia?
Hi, I am new to 3D printing, but I really would like to make my own printer like you did. Is there anyway you could post a written tutorial of how to do this. The videos are very helpful, but writing is more detailed, like measurements, parts, names, prices, places you can buy them, etc. This would be great! I would read the whole thing and start building!
Thank you in advance! your videos are awesome! and I can't wait to start
There are instructions on the Thingiverse page.
Ho there im a long time viewer first time commenter . I work for a bearing company. .. the black material is teflon have you tried using them on the liniar rail ?
What about printing your own bushings? Have you considered it?
I've tried some LM8UU PLA printed, and seems to work fine (just tried without putting it into the actual printer)
Cheers!
You would need a tap to cut the metric acme thread, but it's possible...
- Eddy
I was thinking more in replacing the LM bushings by printed ones than the Z nut... perform the drill could be tricky....
glue the eigus bearing in
Tech2C i want to know what happens when you slap a AZSMZ mini(32bit controller) on it would it print faster and better? the chinese version on aliexpress is $48 us
Yes I'd like to switch to 32bit. I haven't decided which board to purchase as of yet, but the price of that one is compelling.
keep us updated ;) I'm definitely building one of these hypercubes because I've been looking for a sturdy Ridgid affordable diy printer.
Tech2C I am so excited to make this printer. but my only concern is how often parts are tweaked. I'm not saying change is a bad things but my suggestion is change your system to have "stable" and "beta" releases. Pretty much like code. I think advantages here are you can upgrade all the things at once when a new "stable" release comes or or you can slowly change the printer every time a "beta" release comes out. Just a suggestion but I really love what you are doing here, keep up the great work.
The old parts are available. New parts are labeled with a new version number, like 1.1, 1.2 etc...
So just print all the latest ones or all 1.0s etc... However you like.
I'm going to move the older versions to another page so the main Hypercube page is current and without clutter. This video didn't introduce any new part iterations but I understand what you mean. I have no plans or intention to radically change the Hypercube as it is, just minor tweaks as time goes by. Either way no matter which parts you use it will work great.
Tech2C Thanks! I know this video didn't have any new parts but I didn't want to go comment on an old video :P.
The problem that I find with those nut blocks is that I use TR8x2 acme threaded rods and they all seem to want TR8x8 which simply will not do.
I agree, especially when Banggood now offer 8mm lead-screws with pitches down to 1mm!
Tech2C
1mm is over kill for a 3d printer but why haven't the blocks kept up? Sad really.
I've noticed you've been updating files on thingiverse but are you leaving the old files up as well? (V1, V1.1, etc...)
Yes, but I plan to move the older versions to a another page.
Tech2C I'd love to see a Hypercube with dual linear rails on the XY. All I need to do is learn 3d modeling. No biggie :D
tech2c. how do i contact you about printing parts for this printer
Send me a private message.
Could I use parts from my Anet A8 to build this printer?
Yes you can!
Tech2C sweet, gonna start printing!
Cool. But the polymer bearings wear out. A good set of linear bearings should never wear out the rails, if this is happening you have very poor bearings or an improper pairing of metals.
The best threaded rods are ball-screws!!! zero backlash!
Agreed.
igus bearings for 8mm rod *gap********gap* maby you can put in the circle groove of the igus bearing a set ring so they dont slide out any more
would anybody be able to 3d print out the plastic parts and setup an ebay listing?
I can do something similar. I have a 3DHubs page and will be glad to print the parts for you. PM me to set that up.
EDIT: I feel the need to clarify this. Tech2C releases his designs on Thingiverse under a Creative Commons Non-Commercial license, which makes it illegal to print sets out and offer them for sale on eBay. Selling them as objects is a violation of his intellectual property.
The kosher way of doing this is to hire it done from a 3D printing service, such as myself. In this case, you aren't buying a good, you're hiring a service. I am not a lawyer and this is not legal advice, but it is common practice in the 3D printing community. If you can buy a printer and print them, it should follow that you can rent a printer and print them.
I offer you my services on the condition that Tech2C does not object to this use of his intellectual property.
The Garden of Eatin thank you for the offer and thank you for giving that clarification. I used the incorrect terms when referring to "purchasing the parts" when I should have said "can somebody print these out for me as a service" Now that's out the way, can you provide your 3d hubs page and Ill compare prices to some of the 3dhubs around me? thanks in advance
TH-cam doesn't let you post hyperlinks in comments, I'll direct message you.
Except there isn't a way to do that, either. Search for Adam's Hub around Fayetteville NC. If you find a better price, let me know, I'll see if I can match it.
The reason the igus bushings weren't working for you was because you were using them completely incorrectly. They aren't drop-in LM8UU replacements and if you'd bothered to read the specifications you'd know that they have to be preloaded by pressing them into a hole with the specified diameter and tolerances or by using one of the (stupidly overpriced) aluminium shells they sell for exactly this.
Why do you need to lubricate metal to metal and not metal to plastic ?
Some plastics do require lubrication when used with metal... take a look in an older CD player for example. And in the case of metal on metal, sometimes these are not (obviously) lubricated, eg. oilite sintered bronze bearings do not need lubrication as it's built into the design of the bearing.
So it's not a black and white issue. It comes down to materials engineering. Know the materials and what they need for lubrication if any.
Just my $0.02 anyways.
- Eddy
Why not just superglue the IGUS bearings into the housings and then you don't need to screw them down tight.
Now that is thinking outside the box!
apparently you can also get the IGUS bearings in a metal can but i have never seen it. myself i am going to go with bronze bushing in a holder for everything
Found the ones in a can www.igus.co.uk/wpck/2292/drylin_r_rjum_01 not cheap , but they do 8 and 10 mm versions , you can even get the more expensive " reduced pay " version for 10mm that would solve any issues with the carriage on the x www.igus.co.uk/wpck/7676/DryLin_R_RJUM_11 , again not in any way cheap :).
Still think best price per performance is the bonze bushing in a holder.
As long as they are quiet and give about the same or better performance to a standard lm8luu or lm8uu then i am happy.
Lol I got that same oil
Did you see this solution?, I think is the way to go. "It's better to pull than to push". Remember that commercial from Dodge, when the first K cars came? Check the Z axis. th-cam.com/video/5SOvJisTPNc/w-d-xo.html
That plastic is not better than a proper anti backlash lead screws nut fitting.... Why do people always try to improve in procen designs. It may be because people only shop on eBay for these things and not properly sourcing parts
My printer ist based on the Rj4jp's from igus. At first I noticed the sticky behavior too. When you use two on top of each other it getting worse. But if you let them run for a while they getting quite good. In the end I use Rj series which come in a aluminum housing for my new printer.
I found using 2 in series increased friction because the XY Joiner isn't aligning them perfectly. I'd need to print a housing especially for them just like the dual_bushing_holder on the X axis.